Modular earth retaining walls are commonly used for architectural and site development applications. Such walls are subjected to very high pressures exerted by lateral movements of the soil, temperature and shrinkage effects, and seismic loads. Therefore, the backfill soil typically must be braced with tensile reinforcement members. Usually, elongated structures, commonly referred to as geogrids or reinforcement fabrics, are used to provide this reinforcement. Geogrids are often configured in a lattice arrangement and are constructed of a metal or polymer while, reinforcement fabrics are constructed of a woven or nonwoven polymer fiber. These reinforcement members typically extend rearwardly from the wall and into the soil to stabilize the soil against movement and thereby create a more stable soil mass which results in a more structurally secure retaining wall.
Although several different forms of reinforcement members have been developed, difficulties remain with respect to attachment of the members to retaining walls. In particular, the reinforcement members can shift out of position and be pulled out from the retaining wall due to movement of the soil. This difficulty can be especially problematic in areas of high seismic activity. In response to this problem, several current retaining wall systems have been developed to retain geogrid reinforcement members. Rake shaped connector bars are transversely positioned in the center of the contact area between adjacent stacked blocks with the prongs of the connector bar extending through elongated apertures provided in the geogrid to retain it in place. Despite adequately holding the geogrid in position under normal conditions, this system of attachment provides a substantial drawback. Specifically, the geogrids of the system only extend along the back halves of the contact areas between the blocks. Although the geogrids are relatively thin, this partial insertion of the geogrids can cause the retaining wall to bow outwardly due to the aggregate thickness of the geogrids. As can be appreciated, this outward bowing can be substantial with tall retaining walls that require a multiplicity of geogrids. Aside from creating the impression of instability, this condition increases the likelihood of wall failure, particularly in response to seismic activity.
Another problem associated with the construction of modular retaining walls is securement of the blocks to each other within the wall. Various connection methods are currently used in retaining wall construction to interlock the blocks. In one known system, blocks having bores inwardly extending within their top and bottom surfaces are provided for the receipt of dowels or pins. In addition to limiting shifting of the blocks, these pins are used to retain geogrids. Where a geogrid is to be inserted between two courses of stacked blocks, the pins are inserted into the bores with the pins extending through the apertures of the geogrid. Although providing some resistance against block shifting, the actual strength of the block-to-block connection is generated by the friction between the block surfaces. Therefore, shifting can occur. Moreover, the pins do not lock the upper blocks to the lower blocks. Accordingly, severe seismic activity can cause the upper blocks to jump from their foundations and topple downward. Additionally, when the pins are made of metal, they will corrode over time due to the infiltration of moisture from the surrounding environment.
In another known retaining wall, an upper surface of the blocks includes a projection and a lower surface of the blocks includes a cavity into which the projection can extend. Although the provision of these projections and cavities avoids the corrosion problem associated with the pins of the previously described system, similar to that system, no positive locking mechanism is provided to retain the upper blocks on top of the lower blocks. Therefore, this system is susceptible to toppling in response to strong seismic activity. In addition, construction of the walls is complicated by the fact that the top course of blocks must be held in place when the backfill soil is poured to prevent the blocks from being pushed over the edge of the wall.
It can therefore be appreciated that there exists a need for a mechanically stabilized wall system having secure retaining means for maintaining reinforcement members in their proper positions within the wall. Accordingly, it is to the provision of such an improved mechanically stabilized retaining wall system that the present invention is directed.